1. Field of the Invention
The present invention relates to air control valves and more particularly to a positive shut-off air outlet suitable for use in aviation applications.
2. The Prior Art
Air outlets used as passenger and pilot amenities in general aviation provide for air flow at relatively low back pressure compared to those used in commercial aviation. This class of products has suffered from the lack of an effective sealing mechanism and depends on low back pressure to keep leakage levels acceptable. Normal tolerance variation of the components together with the application of surface finish further reduces the manufacturing yield and performance of these air outlets in the closed position.
Products currently available usually employ a xe2x80x9cbutterflyxe2x80x9d or xe2x80x9cdisc typexe2x80x9d valve in which a disc with rounded edges rotates within a nozzle. The best seal is achieved when the disc is matched to the nozzle in size, the axle pins are exactly at their design location, and axle pin holes in the nozzles are also perfectly placed. As the disc varies smaller or the nozzle larger, the air outlet suffers increased leakage. If the variation is reversed, the outlet cannot be assembled. When hole or pin locations vary, the outlet may not close completely.
A positive shut-off air outlet is provided for use, for example, as a passenger or pilot amenity in general aviation, which allows for a contact shut off of the air outlet. The outlet also decreases the dependence on tight design tolerances and improves reliability for closed performance as well as manufacturability.
The outlet includes a nozzle having an internal surface with a spherical radius of curvature and axle openings disposed in the internal surface. A disc is mounted for rotation and longitudinal movement within the nozzle. The disc has an external surface with a spherical radius of curvature adapted to interface with the internal surface of the nozzle. A plurality of axle pins are disposed in the external surface of the disc. Preferably, the nozzle has an external surface and is rotatably mounted within a ball housing, the axle pins extend beyond the external surface of the nozzle, and a seal encircles the nozzle and the ball housing at a point where the axle pins extend. A seal between the ball housing and a mounting flange may also be provided. The disc is mounted for rotation and longitudinal movement between open positions permitting air flow and a closed position preventing air flow. In the closed position, air flow causes longitudinal movement of the disc against the nozzle so that the external surface of the disc interfaces with the internal surface of the nozzle to form an air flow seal. Preferably, an actuator coupled to the disc rotates the disc between any of the open positions and the closed position.
The ball housing preferably has two diametrically opposed longitudinal slots in the back edge of the ball housing. The disc preferably has an outside radius and an edge radius equal to or slightly smaller than the internal spherical radius of the nozzle. Preferably, the nozzle has an exit end with a spherical internal surface that provides a smaller diameter than that of the remainder of the nozzle.
Each axle pin is received within a respective axle opening disposed in the internal surface of the nozzle. Each axle opening is dimensioned to permit longitudinal movement of a respective axle pin and the disc in the nozzle.
Both seals are preferably formed from polymerized tetrafluoroethylene (Teflon) and are adapted to rotate with the nozzle inside the ball housing.